A healthy left ventricle of a human heart, which is the primary pumping chamber, is generally conical or apical in shape in that it is longer (along a longitudinal axis extending in a direction from the aortic valve to the apex) than it is wide (along a transverse axis extending between opposing walls at the widest point of the left ventricle) and descends from a base with a decreasing cross-sectional circumference to a point or apex. The pumping of blood from the left ventricle is accomplished by a squeezing motion and a twisting or torsional motion.
The squeezing motion occurs between the lateral wall of the left ventricle and the septum. The twisting motion is a result of heart muscle fibers that extend in a circular or spiral direction around the heart. When these fibers contract, they produce a gradient of angular displacements of the myocardium from the apex to the base about the longitudinal axis of heart. The resultant force vectors extend at angles from about 30 to 60 degrees to the flow of blood through the aortic valve. The contraction of the heart is manifested as a counterclockwise rotation of the apex relative to the base, when viewed from the apex. A healthy heart can pump blood from the left ventricle in a very efficient manner due to the spiral contractility of the heart.
Chronic congestive heart failure and other disease processes can cause the heart to enlarge or dilate from a conical shape to a shorter and wider shape, which in turn causes the muscle fibers to become reoriented. As a result of the dilation, the orientation of the muscle fibers produces lines of force directed generally laterally of the left ventricle at about 90 degrees relative to the outward flow of the blood. Hence, blood is pushed inwardly (toward the center of the left ventricle), rather than at an acute angle relative to the outward blood flow, thereby greatly reducing the pumping efficiency of the left ventricle. In a similar manner, dilation of the heart also can adversely affect the function of the right ventricle.
A variety of treatment procedures have been proposed over the years for treating left ventricular dilatation. However, these procedures typically involve radical open-heart surgeries designed to surgically reduce the volume of the left ventricle. In recent years, several new minimally invasive techniques for improving heart function have been proposed that do not require opening the chest or cardiopulmonary by-pass. However, none of these procedures has gained widespread acceptance and most fail to address the underlying cause of the problem.
Accordingly, an urgent need exists for a new device and method for treating left ventricular dilatation.